Showing papers on "Graphite published in 1978"
TL;DR: In this article, an extensive survey of the Raman spectral activity of a wide variety of carbon materials has produced experimental evidence for at least five structure-sensitive lines or bands or bands.
Abstract: An extensive survey of the Raman spectral activity of a wide variety of carbon materials has produced experimental evidence for at least five structure-sensitive lines or bands. In addition to the well-known, always present 1580 cm−1 graphite line and the 1360 cm−1 disordered carbon line, there is a disorder line at ∼1620 cm−1 that is responsible for the apparent blue-shift of the graphite line in very disordered carbons; and there are lines at ∼2700 and ∼2735 cm−1 that are strong in graphite and annealed carbons but absent in very disordered carbons. These additional lines increase the capability of Raman spectroscopy to characterize carbon materials.
291 citations
254 citations
TL;DR: In this paper, structural changes in natural graphite with grinding were studied by Raman spectroscopy along with X-ray diffraction, and a linear relationship was obtained for the ground graphite when the relative intensity of the 1360 cm−1 band is plotted as a function of effective Debye parameter.
166 citations
TL;DR: Ion beam studies of the reactions between nitrogen and surfaces of Group IV elements and their oxides resulting in nitride formation are reported in this article, where the products induced by 500 eV N 2 + + beams on diamond, graphite and elemental Si, Ge, Sn, Pb and oxides.
139 citations
TL;DR: In this article, the effects of Li, Na and K carbonates in catalyzing the reaction between graphite and water vapor have been studied in the temperature range 700-1100°C, using simultaneous thermogravimetry-differential thermal analysis.
117 citations
104 citations
TL;DR: In this paper, a carbon paste electrode containing chemically modified graphite has been fabricated and applied to the analysis of silver ion in aqueous media and it is shown that one can preconcentrate and then analyze for metal ions at low concentrations using these electrodes.
Abstract: A carbon paste electrode containing chemically modified graphite has been fabricated and applied to the analysis of silver ion in aqueous media Utilizing complexation and subsequent precipitation steps, it is shown that one can preconcentrate and then analyze for metal ions at low concentrations using these electrodes
102 citations
TL;DR: In this paper, the carbon $K$ edge in graphite was measured using inelastic-electron-scattering spectroscopy and the extended x-ray absorption fine structure was in good agreement with theory for the first-neighbor atoms at a distance of 1.42 \AA{}.
Abstract: We have measured the carbon $K$ edge in graphite using inelastic-electron-scattering spectroscopy. The extended x-ray absorption fine structure is in good agreement with theory for the first-neighbor atoms at a distance of 1.42 \AA{}. The momentum dependence of the edge structure is in qualitative agreement with a simple band-structure picture. A comparison of the signal counting rates for electron-energy-loss and photoabsorption experiments shows that the energy-loss method is competitive with synchrotron radiation sources up to about 1000 eV.
100 citations
96 citations
90 citations
TL;DR: In this article, the electronic properties of the regular graphite lattice are investigated within self-consistent LCAO (linear combination of atomic orbitals) scheme based as a modified extended-H\"uckel approximation.
Abstract: The electronic properties of the regular graphite lattice are investigated within self-consistent LCAO (linear combination of atomic orbitals) scheme based as a modified extended-H\"uckel approximation. The band structure and interband transition energies agree favorably with previous first-principles calculations. Good agreement with experimental data on the density of valence states, energetic position of the lowest conduction states, equilibrium unit-cell parameters, cohesive energy and vibration force constants, is obtained. The McClure band parameters that were previously adjusted to obtain agreement with Fermi-surface data and the electronic specific heat, are reasonably reproduced. The charge distribution and bonding characteristics of the covalent graphite structure, are discussed. The same calculation scheme is used in part II of this article (following paper) to discuss properties associated with point defects in graphite. The correlation between the electronic properties of the regular and point-defect-containing lattice is studied.
TL;DR: In this paper, the effect of electropolymerization on the interfacial properties of the resulting composite was manifested in variations of the measured interlaminar shear and impact strengths of the composite specimens.
Abstract: The electrodic polymerization on graphite fibers of a variety of monomers having different types of functional groups has been investigated. In addition to vinyl polymerization, some novel polymerizations of cyclic functional groups have been conducted under appropriate polymerization conditions. In many instances, the grafting of the surface polymer to the fiber has been confirmed. The stereochemical configuration of poly(methyl methacrylate) resulting from electropolymerization was measured, but conclusive evidence could not be obtained for the occurrence of stereo-regulation in electrochemical polymerization on graphite fiber surface; Composite specimens were prepared by the incorporation of the coated fibers in an epoxy matrix. It was demonstrated that the effect of electropolymerization on the interfacial properties of the resulting composite was manifested in variations of the measured interlaminar shear and impact strengths of the composite specimens. The increase or decrease in interlaminar shear was accompanied by the usually observed reverse change in impact strength. In exception to this general trend, it was also indicated that the shear and impact strengths could simultaneously be increased. Implicit in these findings is the contribution of the electrochemically formed interlayer to one or more of the toughening mechanisms that are available to fiber reinforced composites. The potential value of interphase modification by electrochemical polymerization is thus clearly indicated.
TL;DR: In this paper, it was shown that Ni3C formed in this manner extends from the surface to close to the interface, and a model was proposed to explain the mechanism of Ni3c formation.
TL;DR: In this article, the authors measured diffraction patterns of thermal He atoms from a low-temperature graphite surface and showed that the repulsive part of the periodic gas-surface potential is rather well represented by the first Fourier component.
Abstract: Scattering of thermal He atoms from a low-temperature graphite (0001) surface was carried out. The measured diffraction pattern shows that the repulsive part of the periodic gas-surface potential is rather well represented by the first Fourier component. The "hard wall" peak-to-peak spatial modulation is 0.21 \AA{}. Bound-state resonances allow one to determine four distinct energy levels of the laterally averaged potential well. A comparison with available adsorption data is presented.
TL;DR: In this article, a thin mat of fine fibres and crystallites has been found on the surfaces of graphite and carbon anodes after low current arc operation in nitrogen, and it is found that conduction through the fibre layer and a porous layer beneath the fibres controls the cooling rate for the first 100 μs.
TL;DR: In this paper, the susceptibility of oxygen adsorbed on graphite indicates that magnetic transitions are present even in films of submonolayer thickness, which strongly supports the supposition that antiferromagnetic order can only be present simultaneously with configurational order.
Abstract: The susceptibility of oxygen adsorbed on graphite indicates that magnetic transitions are present even in films of submonolayer thickness. This result contrasts with previous work on amorphous oxygen films and strongly supports the supposition that antiferromagnetic order can only be present simultaneously with configurational order.
TL;DR: The first example of a first-stage boron nitride salt was reported in this article. But this was a first stage graphite salt, and it was not the first instance of a borone nitride (BN)4+SO3F.
Abstract: Graphite is oxidized by O2+AsF6– and by OsF6 to give first-stage graphite salts C8+MF6–; S2O6F2 oxidizes both graphite and boron nitride to yield the salts C12+-SO3F– and (BN)4+SO3F–, the latter being the first example of a first-stage boron nitride salt.
TL;DR: In this paper, the Raman spectra of single crystals and powder of hexagonal boron nitride have been measured at room temperature and two Raman lines due to phonons of 52.5 and 1366 cm-1 were observed.
TL;DR: In this paper, a study of the surface area loss surface area of platinum when supported on both untreated and oxidized graphitized carbon black was conducted, where the treatment of the graphite support was found to affect the rate of Pt area loss in a hot, concentrated H3PO4 solution with the support prepared using the iron oxide catalysed oxidation of graphite.
TL;DR: In this article, it was shown that gas-phase intercalation of graphite by nitric acid is accompanied by evolution of a brown gas which has been identified as nitrogen dioxide by chemiluminescence measurements.
TL;DR: In this paper, the sputtering yields of graphite, B4 C, SiC and TiC have been measured at normal incidence for H, D and 4He ions in the energy range between 100 and 8 keV.
TL;DR: In this article, the graphite particles were made by pressing mixtures of nickel- or copper-coated particles and aluminium powders together at pressures varying between 2 and 20 kg mm-2, until the particles disintegrated and the powders were dispersed.
Abstract: Copper- and nickel-coated graphite particles can be successfully introduced into aluminium-base alloy melts as pellets to produce cast aluminium-graphite particle composites. The pellets were made by pressing mixtures of nickel- or copper-coated graphite particles and aluminium powders together at pressures varying between 2 and 20 kg mm–2. These pellets were dispersed in aluminium alloy melts by plunging and holding them in the melts using a refractory coated mild steel cone, until the pellets disintegrated and the powders were dispersed. The optimum pressure for the preparation of pellets was 2 to 5 kg mm–2 and the optimum size and percentage of aluminium powder were 400 to 1000mgrm and 35 wt% respectively. Under optimum conditions the recovery of the graphite particles in the castings was as high as 96%, these particles being pushed into the last freezing interdendritic regions. The tensile strength and the hardness of the graphite aluminium alloys made using the pellet method are comparable to those of similar composites made using gas injection or the vortex method. The pellet method however has the advantage of greater reproducibility and flexibility. Dispersion of graphite particles in the matrix of cast aluminium alloys using the pellet method increases their resistance to wear.
TL;DR: Relative inelastic mean free paths (λ) for 1000-eV electrons have been determined for a number of polymers and other materials (relative to 967 eV electrons in graphite) using X-ray photoelectron spectroscopy.
TL;DR: The electrical conductivity of battery materials, e.g. manganese dioxide, carbon black, graphite, black mix, etc., has been measured in battery labo as mentioned in this paper.
TL;DR: In this article, the experimental conditions which induce graphite surface contamination were determined by using the gold decoration technique under ultra-high vacuum (UHV) and showed that gas adsorption on clean graphite surfaces depends on the degree of ionization of the gas.
Patent•
15 Nov 1978
TL;DR: In this article, a method of homogeneously mixing boron carbide in submicron powder form with small quantities of a carbon containing additive, forming the powder mixture into a shaped green body and then sintering the body in a controlled atmosphere and in the absence of external pressure at a temperature of about 2100°-2200° C.
Abstract: A method of producing dense shaped articles of pure boron carbide that optionally contain 0.1 to 8% by weight of free carbon in the form of graphite is disclosed involving the steps of homogeneously mixing boron carbide in submicron powder form with small quantities of a carbon containing additive, forming the powder mixture into a shaped green body and then sintering the body in a controlled atmosphere and in the absence of external pressure at a temperature of about 2100°-2200° C. The shaped articles thus obtained are polycrystalline and, insofar as they correspond to the stoichiometric composition B 4 C, single-phase; they have an average grain size of not more than 10 μm, a density of at least 90% of the theoretical density of boron carbide and a flexural strength of at least 300 N/mm 2 . The fracture mode of the sintered articles is completely transcrystalline.
TL;DR: Ion beam studies of the interactions of Ar+ and Xe+ with surfaces of pyrolytic graphite, graphite monofluoride and teflon are reported in this article.